What Is a Sterile Filter?

A sterile filter is a synthetic membrane designed to prevent the movement of particles, including bacterium and proteins, from one reservoir to another. Nearly every aspect of medical treatment includes the use of a sterile filter. Some of these filters are designed to be used multiple times after re-sterilization, and others are only approved for a single use.

Many aqueous sterile filters are made from a mixture of a cellulose material called esters (MCE). Polyethersulphone (PES) and a nylon polyesteramide are also commonly used in the production of the filter membrane and are often used for dry air filtration. If a sterile filter is not specifically recommended for use with liquids, care should be taken to avoid any contact with aqueous substances.

One type of sterile filter is used in the compressed air pumps utilized in many medical facilities. Most of these air filters can be sterilized in an autoclave at least 100 times before it is necessary to replace the filter. The size of the filter is determined by the amount of air pressure that is expected to flow through the filter.

Compressed sterile air filters are sometimes used to create what is known as a clean room, free of bacteria and other harmful particulates, for people with compromised immune systems. Individual air supply pumps are also equipped with a sterile air filter to ensure the delivery of contaminant-free air. These air filters are often sterilized by gamma radiation and packaged individually.

Sterile filters can be placed inside syringes used for injecting or removing fluid from the body. The syringe filter is commonly used when collecting blood and certain tissues for the preparation of a diagnostic culture. This sterile filter may also be used to separate some enzymes and proteins from fluids aspirated from the patient. A syringe filter is usually packaged for a single use and should be disposed of with the used syringe in an appropriate waste receptacle.

A sterile filter may used for point-of-use (POU) water filtration for use by a person with a compromised immune system. Many skilled nursing facilities have installed POU water filtration systems in the individual rooms as well as the food preparation areas. Most POU sterile filters are disposable and designed for easy removal and replacement.

POU water filtration systems are also installed in the homes of persons with a lowered immune response. The advanced filtration may contribute to improved health and less incidence of infections. A sterile filter within the POU will need to be replaced after continued use.